This invention relates to a traveling system for mobile bodies and a control method therefor. More particularly, the invention relates to a traveling system for mobile bodies and a control method therefor, having a first and a second mobile bodies for running along a travel path, a first distance detecting device for detecting a distance between a first reference position set to a first end of the travel path and the first mobile body lying adjacent the first reference position, a second distance detecting device for detecting a distance between a second reference position set to a second end of the travel path and the second mobile body lying adjacent the second reference position, and a control device for controlling traveling operations of the first and second mobile bodies, respectively, based on detection information from the first and second distance detecting devices.
The traveling system for the mobile bodies noted above is applicable to an automatic warehouse facility, for example. The control device controls traveling operations of stacker cranes or automatic transport carriages acting as an example of a pair of mobile bodies, to transport articles with the pair of mobile bodies.
The control device is configured to run each mobile body to a target traveling position based on detection information from the first distance detecting device and second distance detecting device. When one of the mobile bodies controlled to move to a target traveling position is likely to interfere with the other mobile body, the latter is shunted aside, for example. In this way, each mobile body is caused to move while avoiding a situation where the two mobile bodies are spaced away from each other by less than an allowable distance.
In a conventional example of traveling system for the above mobile bodies, in order to avoid a collision between the mobile bodies when an abnormality occurs with the control device or distance detecting devices so that traveling operations of the mobile bodies are not controlled appropriately, each of the first and second mobile bodies includes a relative distance detecting device for optically detecting a distance to the other mobile body, and a control device for monitoring the distance between the mobile bodies based on the detection information from the relative distance detecting device. When the control device provided on each mobile body for monitoring the distance between the mobile bodies determines that the distance between the mobile bodies is less than a predetermined allowable distance, an emergency stopping process is carried out to stop power supply to a propelling device, thereby to bring the mobile body to an emergency stop (see Japanese Unexamined Patent Publication No. 2006-044935, for example).
The apparatus disclosed in the above document allows mutual communication between the control devices provided on the mobile bodies for monitoring the distance between the mobile bodies. When the distance between the mobile bodies becomes shorter than the allowable distance, each of the control devices provided on the mobile bodies transmits stop command information to the control device on the other mobile body, to stop both of the mobile bodies moving abnormally close to each other. With such construction, even when an abnormality occurs with the relative distance detecting device of one of the mobile bodies moving abnormally close to each other, both of the first and second mobile bodies can be stopped reliably to prevent a collision between the mobile bodies.
In the apparatus disclosed in the above document, what correspond to the first distance detecting device and second distance detecting device are position detecting sensors arranged in opposite end regions of a travel path. Although not expressly stated in the above document, such position detecting sensors generally comprise optical distance sensors, such as laser ranging sensors, which detect traveling positions on the travel path of the mobile bodies by measuring distances between a reference position on the ground and the mobile bodies. A ground controller is provided on the ground to act as the control device. The ground controller is connected to the position detecting sensors through cables (or wires). The ground controller controls traveling operations of the first and second mobile bodies based on traveling position information about the mobile bodies which is detection information from the position detecting sensors.
In the above conventional traveling system for the mobile bodies, in order to avoid a collision between the mobile bodies when an abnormality occurs with the control device or distance detecting devices, each of the first and second mobile bodies needs to have the relative distance detecting device for detecting a distance to the other of the first and second mobile bodies, and the control device for monitoring the distance between the mobile bodies based on the detection information from the relative distance detecting device. Therefore, the construction of each mobile body becomes complicated and expensive, and the construction of the entire system having a pair of such mobile bodies also becomes complicated and expensive.
With the above conventional traveling system for the mobile bodies, the control devices provided on the respective mobile bodies for monitoring the distance between the mobile bodies must be constructed capable of communicating with each other, in order to stop reliably both of the first and second mobile bodies moving abnormally close to each other even when one of the relative distance detecting devices breaks down. In this regard also, the construction of each mobile body becomes complicated and expensive, and the construction of the entire system becomes complicated and expensive.